Re: [edk2-devel] [PATCH 0/2] AmdSev: Harden SEV Kernel hashes verifier

["Aithal, Srikanth via groups.io" <srikanth.aithal=amd.com@groups.io>]

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Hello,

SEV/SEVES guest boot fails with AMDSEV OVMF package built using upstream 
edk2 master [commit head: 2fbaaa96d11ad61a9133df1728e3fe965d1457a5].

SEV/SEVES guest boot with AMDSEV package gets stuck at below point:

Plain Text

|2024-06-26 04:38:02: FetchBlob: loading 14332416 bytes for "kernel" 
2024-06-26 04:38:02: Select Item: 0x18 2024-06-26 04:38:02: Select Item: 
0x11 2024-06-26 04:38:02: VerifyBlob: Found GUID 
4DE79437-ABD2-427F-B835-D5B172D2045B in table 2024-06-26 04:38:02: 
VerifyBlob: Hash comparison succeeded for "kernel" 2024-06-26 04:38:02: 
Select Item: 0xB 2024-06-26 04:38:02: VerifyBlob: Found GUID 
44BAF731-3A2F-4BD7-9AF1-41E29169781D in table 2024-06-26 04:38:02: 
VerifyBlob: Blob Specified in Hash Table was not Provided --> Hung here |

This was working until yesterday [commit head: be38c01], where we can 
see boot was proceeding

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|2024-06-25 03:13:23: VerifyBlob: Found GUID 
4DE79437-ABD2-427F-B835-D5B172D2045B in table 2024-06-25 03:13:23: 
VerifyBlob: Hash comparison succeeded for "kernel" 2024-06-25 03:13:23: 
Select Item: 0xB 2024-06-25 03:13:23: VerifyBlob: Found GUID 
44BAF731-3A2F-4BD7-9AF1-41E29169781D in table 2024-06-25 03:13:23: 
VerifyBlob: Hash comparison succeeded for "initrd" 2024-06-25 03:13:23: 
Select Item: 0x14 2024-06-25 03:13:23: FetchBlob: loading 120 bytes for 
"cmdline" 2024-06-25 03:13:23: Select Item: 0x15 2024-06-25 03:13:23: 
VerifyBlob: Found GUID 97D02DD8-BD20-4C94-AA78-E7714D36AB2A in table 
2024-06-25 03:13:23: VerifyBlob: Hash comparison succeeded for "cmdline"|


After this patch got merged the regression is seen.

Thanks,

Srikanth Aithal


On 5/7/2024 1:57 AM, Tobin Feldman-Fitzthum via groups.io wrote:
> The AmdSev package has a so-called BlobVerifier, which
> is meant to extend the TCB of a confidential guest
> (SEV or SNP) to include components provided via fw_cfg
> such as initrd, kernel, kernel params.
>
> This series fixes a few implementation errors in the
> blob verifier. One common theme is that the verifier
> currently fails to halt the boot when an invalid blob
> is detected. This can lead to a confidential guest
> having a launch measurement that does not reflect the
> guest TCB.
>
> This series could also help us move towards consolidating
> the AmdSev package back into the OvmfPkg although more
> discussion will be needed on this.
>
> Thank you for Ryan Savino at AMD for pointing out
> some of these issues.
>
> Tobin Feldman-Fitzthum (2):
>    AmdSev: Rework Blob Verifier
>    AmdSev: Halt on failed blob allocation
>
>   .../BlobVerifierSevHashes.c                   | 56 ++++++++++++++++---
>   OvmfPkg/Include/Library/BlobVerifierLib.h     | 14 +++--
>   .../BlobVerifierLibNull/BlobVerifierNull.c    | 13 +++--
>   .../QemuKernelLoaderFsDxe.c                   |  9 ++-
>   4 files changed, 69 insertions(+), 23 deletions(-)
>


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